Internet Engineering Task Force (IETF) R. Asati
Request for Comments: 6201 C. Pignataro
Updates: 1242, 2544 F. Calabria
Category: Informational Cisco
ISSN: 2070-1721 C. Olvera
Consulintel
March 2011
Device Reset Characterization
Abstract
An operational forwarding device may need to be restarted
(automatically or manually) for a variety of reasons, an event called
a "reset" in this document. Since there may be an interruption in
the forwarding operation during a reset, it is useful to know how
long a device takes to resume the forwarding operation.
This document specifies a methodology for characterizing reset (and
reset time) during benchmarking of forwarding devices and provides
clarity and consistency in reset test procedures beyond what is
specified in RFC 2544. Therefore, it updates RFC 2544. This
document also defines the benchmarking term "reset time" and, only in
this, updates RFC 1242.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6201.
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Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
1.1. Scope ......................................................3
1.2. Reset Time .................................................4
1.3. Reset Time Measurement Methods .............................5
1.4. Reporting Format ...........................................6
2. Key Words to Reflect Requirements ...............................7
3. Test Requirements ...............................................7
4. Reset Tests .....................................................8
4.1. Hardware Reset Tests .......................................9
4.1.1. Routing Processor (RP) / Routing Engine Reset .......9
4.1.2. Line Card (LC) Removal and Insertion (REQUIRED) ....11
4.2. Software Reset Tests ......................................12
4.2.1. Operating System (OS) Reset (REQUIRED) .............12
4.2.2. Process Reset (OPTIONAL) ...........................13
4.3. Power Interruption Test ...................................14
4.3.1. Power Interruption (REQUIRED) ......................14
5. Security Considerations ........................................15
6. Acknowledgments ................................................16
7. References .....................................................16
7.1. Normative References ......................................16
7.2. Informative References ....................................16
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1. Introduction
An operational forwarding device (or one of its components) may need
to be restarted for a variety of reasons, an event called a "reset"
in this document. Since there may be an interruption in the
forwarding operation during a reset, it is useful to know how long a
device takes to resume the forwarding operation. In other words, the
duration of the recovery time following the reset (see Section 1.2,
"Reset Time") is what is in question.
However, the answer to this question is no longer simple and
straightforward as the modern forwarding devices employ many hardware
advancements (distributed forwarding, etc.) and software advancements
(graceful restart, etc.) that influence the recovery time after the
reset.
1.1. Scope
This document specifies a methodology for characterizing reset (and
reset time) during benchmarking of forwarding devices and provides
clarity and consistency in reset procedures beyond what is specified
in [RFC2544]. Software upgrades involve additional benchmarking
complexities and are outside the scope of this document.
These procedures may be used by other benchmarking documents such as
[RFC2544], [RFC5180], [RFC5695], etc., and it is expected that other
protocol-specific benchmarking documents will reference this document
for reset recovery time characterization. Specific Routing
Information Base (RIB) and Forwarding Information Base (FIB) scaling
considerations are outside the scope of this document and can be
quite complex to characterize. However, other documents can
characterize specific dynamic protocols' scaling and interactions as
well as leverage and augment the reset tests defined in this
document.
This document updates Section 26.6 of [RFC2544] and defines the
benchmarking term "reset time", updating [RFC1242].
This document focuses only on the reset criterion of benchmarking and
presumes that it would be beneficial to [RFC5180], [RFC5695], and
other IETF Benchmarking Methodology Working Group (BMWG) efforts.
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1.2. Reset Time
Definition
Reset time is the total time that a device is determined to be out
of operation and includes the time to perform the reset and the
time to recover from it.
Discussion
During a period of time after a reset or power up, network devices
may not accept and forward frames. The duration of this period of
forwarding unavailability can be useful in evaluating devices. In
addition, some network devices require some form of reset when
specific setup variables are modified. If the reset period were
long, it might discourage network managers from modifying these
variables on production networks.
The events characterized in this document are entire reset events.
That is, the recovery period measured includes the time to perform
the reset and the time to recover from it. Some reset events will
be atomic (such as pressing a reset button) while others (such as
power cycling) may comprise multiple actions with a recognized
interval between them. In both cases, the duration considered is
from the start of the event until full recovery of forwarding
after the completion of the reset events.
Measurement Units
Time, in milliseconds, providing sufficient resolution to
distinguish between different trials and different
implementations. See Section 1.4.
Issues
There are various types of resets: hardware resets, software
resets, and power interruptions. See Section 4.
See Also
This definition updates [RFC1242].
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1.3. Reset Time Measurement Methods
The reset time is the time during which traffic forwarding is
temporarily interrupted following a reset event. Strictly speaking,
this is the time over which one or more frames are lost. This
definition is similar to that of "Loss of Connectivity Period"
defined in [IGPConv], Section 4.
There are two accepted methods to measure the reset time:
1. Frame-Loss Method - This method requires test tool capability to
monitor the number of lost frames. In this method, the offered
stream rate (frames per second) must be known. The reset time is
calculated per the equation below:
Frames_lost (packets)
Reset_time = -------------------------------------
Offered_rate (packets per second)
2. Timestamp Method - This method requires test tool capability to
timestamp each frame. In this method, the test tool timestamps
each transmitted frame and monitors the received frame's
timestamp. During the test, the test tool records the timestamp
(Timestamp A) of the frame that was last received prior to the
reset interruption and the timestamp of the first frame after the
interruption stopped (Timestamp B). The difference between
Timestamp B and Timestamp A is the reset time.
The tester/operator MAY use either method for reset time measurement
depending on the test tool capability. However, the Frame-Loss
method SHOULD be used if the test tool is capable of (a) counting the
number of lost frames per stream and (b) transmitting test frame
despite the physical link status, whereas the Timestamp method SHOULD
be used if the test tool is capable of (a) timestamping each frame,
(b) monitoring received frame's timestamp, and (c) transmitting
frames only if the physical link status is UP. That is, specific
test tool capabilities may dictate which method to use. If the test
tool supports both methods based on its capabilities, the
tester/operator SHOULD use the one that provides more accuracy.
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1.4. Reporting Format
All reset results are reported in a simple statement including the
frame loss (if measured) and reset times.
For each test case, it is RECOMMENDED that the following parameters
be reported in these units:
Parameter Units or Examples
---------------------------------------------------------------
Throughput Frames per second and bits per
second
Loss (average) Frames
Reset Time (average) Milliseconds
Number of trials Integer count
Protocol IPv4, IPv6, MPLS, etc.
Frame Size Octets
Port Media Ethernet, Gigabit Ethernet (GbE),
Packet over SONET (POS), etc.
Port Speed 10 Gbps, 1 Gbps, 100 Mbps, etc.
Interface Encap. Ethernet, Ethernet VLAN,
PPP, High-Level Data Link Control
(HDLC), etc.
For mixed protocol environments, frames SHOULD be distributed between
all the different protocols. The distribution MAY approximate the
network conditions of deployment. In all cases, the details of the
mixed protocol distribution MUST be included in the reporting.
Additionally, the DUT (Device Under Test) or SUT (System Under Test)
and test bed provisioning, port and line-card arrangement,
configuration, and deployed methodologies that may influence the
overall reset time MUST be listed. (Refer to the additional factors
listed in Section 3).
The reporting of results MUST regard repeatability considerations
from Section 4 of [RFC2544]. It is RECOMMENDED to perform multiple
trials and report average results.
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2. Key Words to Reflect Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119]. RFC 2119 defines the use of these key words to help make
the intent of Standards-Track documents as clear as possible. While
this document uses these keywords, this document is not a Standards-
Track document.
3. Test Requirements
Tests SHOULD first be performed such that the forwarding state
re-establishment is independent from an external source (i.e., using
static address resolution, routing and forwarding configuration, and
not dynamic protocols). However, tests MAY subsequently be performed
using dynamic protocols that the forwarding state depends on (e.g.,
dynamic Interior Gateway Protocols (IGP), Address Resolution Protocol
(ARP), PPP Control Protocols, etc.). The considerations in this
section apply.
In order to provide consistence and fairness while benchmarking a set
of different DUTs, the Network tester/operator MUST (a) use identical
control and data plane information during testing and (b) document
and report any factors that may influence the overall time after
reset/convergence.
Some of these factors include the following:
1. Type of reset - hardware (line-card crash, etc.) versus software
(protocol reset, process crash, etc.) or even complete power
failures
2. Manual versus automatic reset
3. Scheduled versus non-scheduled reset
4. Local versus remote reset
5. Scale - Number of line cards present versus in use
6. Scale - Number of physical and logical interfaces
7. Scale - Number of routing protocol instances
8. Scale - Number of routing table entries
9. Scale - Number of route processors available
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10. Performance - Redundancy strategy deployed for route processors
and line cards
11. Performance - Interface encapsulation as well as achievable
throughput [RFC2544]
12. Any other internal or external factor that may influence reset
time after a hardware or software reset
The reset time is one of the key characterization results reported
after each test run. While the reset time during a reset test event
may be zero, there may still be effects on traffic, such as transient
delay variation or increased latency. However, that is not covered
and is deemed outside the scope of this document. In this case, only
"no loss" is reported.
4. Reset Tests
This section contains descriptions of the tests that are related to
the characterization of the time needed for DUTs (Devices Under Test)
or SUTs (Systems Under Test) to recover from a reset. There are
three types of resets considered in this document:
1. Hardware resets
2. Software resets
3. Power interruption
Different types of resets potentially have a different impact on the
forwarding behavior of the device. As an example, a software reset
(of a routing process) might not result in forwarding interruption,
whereas a hardware reset (of a line card) most likely will.
Section 4.1 describes various hardware resets, whereas Section 4.2
describes various software resets. Additionally, Section 4.3
describes power interruption tests. These sections define and
characterize these resets.
Additionally, since device-specific implementations may vary for
hardware and software type resets, it is desirable to classify each
test case as "REQUIRED" or "OPTIONAL".
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4.1. Hardware Reset Tests
A hardware reset test is a test designed to characterize the time it
takes a DUT to recover from a hardware reset.
A hardware reset generally involves the re-initialization of one or
more physical components in the DUT, but not the entire DUT.
A hardware reset is executed by the operator, for example, by
physical removal of a hardware component, by pressing a reset button
for the component, or by being triggered from the command line
interface (CLI).
Reset procedures that do not require the physical removal and
insertion of a hardware component are RECOMMENDED. These include
using the command line interface (CLI) or a physical switch or
button. If such procedures cannot be performed (e.g., because of a
lack of platform support or because the corresponding test case calls
for them), human operation time SHOULD be minimized across different
platforms and test cases as much as possible, and variation in human
operator time SHOULD also be minimized across different vendors'
products as much as practical by having the same person perform the
operation and by practicing the operation. Additionally, the time
between removal and insertion SHOULD be recorded and reported.
For routers that do not contain separate Routing Processor and Line
Card modules, the hardware reset tests are not performed since they
are not relevant; instead, the power interruption tests MUST be
performed (see Section 4.3) in these cases.
4.1.1. Routing Processor (RP) / Routing Engine Reset
The Routing Processor (RP) is the DUT module that is primarily
concerned with Control Plane functions.
4.1.1.1. RP Reset for a Single-RP Device (REQUIRED)
Objective
To characterize the time needed for a DUT to recover from a Route
Processor hardware reset in a single RP environment.
Procedure
First, ensure that the RP is in a permanent state to which it will
return after the reset by performing some or all of the following
operational tasks: save the current DUT configuration, specify
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boot parameters, ensure the appropriate software files are
available, or perform additional operating system or hardware-
related tasks.
Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, perform the Route Processor (RP) hardware reset at this
point. This entails, for example, physically removing the RP to
later re-insert it or triggering a hardware reset by other means
(e.g., command line interface, physical switch, etc.).
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
Reporting Format
The reporting format is defined in Section 1.4.
4.1.1.2. RP Switchover for a Multiple-RP Device (OPTIONAL)
Objective
To characterize the time needed for the "secondary" Route
Processor (sometimes referred to as the "backup" RP) of a DUT to
become active after a "primary" (or "active") Route Processor
hardware reset. This process is often referred to as "RP
Switchover". The characterization in this test should be done for
the default DUT behavior and, if it exists, for the DUT's non-
default configuration that minimizes frame loss.
Procedure
This test characterizes RP Switchover. Many implementations allow
for optimized switchover capabilities that minimize the downtime
during the actual switchover. This test consists of two sub-cases
from a switchover characteristic's standpoint: first, a default
behavior (with no switchover-specific configurations) and,
potentially second, a non-default behavior with switchover
configuration to minimize frame loss. Therefore, the procedures
hereby described are executed twice and reported separately.
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First, ensure that the RPs are in a permanent state such that the
secondary RP will be activated to the same state as the active RP
by performing some or all of the following operational tasks: save
the current DUT configuration, specify boot parameters, ensure the
appropriate software files are available, or perform additional
operating system or hardware-related tasks.
Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, perform the primary Route Processor (RP) hardware reset at
this point. This entails, for example, physically removing the RP
or triggering a hardware reset by other means (e.g., command line
interface, physical switch, etc.). It is up to the operator to
decide whether or not the primary RP needs to be re-inserted after
a grace period.
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
Reporting Format
The reset results are potentially reported twice, one for the
default switchover behavior (i.e., the DUT without any switchover-
specific enhanced configuration) and the other for the switchover-
specific behavior if it exists (i.e., the DUT configured for
optimized switchover capabilities that minimize the downtime
during the actual switchover).
The reporting format is defined in Section 1.4 and also includes
any specific redundancy scheme in place.
4.1.2. Line Card (LC) Removal and Insertion (REQUIRED)
The Line Card (LC) is the DUT component that is responsible for
packet forwarding.
Objective
To characterize the time needed for a DUT to recover from a line-
card removal and insertion event.
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Procedure
For this test, the line card that is being hardware-reset MUST be
on the forwarding path, and all destinations MUST be directly
connected.
First, complete some or all of the following operational tasks:
save the current DUT configuration, specify boot parameters,
ensure the appropriate software files are available, or perform
additional operating system or hardware-related tasks.
Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, perform the Line Card (LC) hardware reset at this point.
This entails, for example, physically removing the LC to later re-
insert it or triggering a hardware reset by other means (e.g.,
CLI, physical switch, etc.).
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
Reporting Format
The reporting format is defined in Section 1.4.
4.2. Software Reset Tests
A software reset test characterizes the time needed for a DUT to
recover from a software reset.
In contrast to a hardware reset, a software reset involves only the
re-initialization of the execution, data structures, and partial
state within the software running on the DUT module(s).
A software reset is initiated, for example, from the DUT's CLI.
4.2.1. Operating System (OS) Reset (REQUIRED)
Objective
To characterize the time needed for a DUT to recover from an
operating system (OS) software reset.
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Procedure
First, complete some or all of the following operational tasks:
save the current DUT configuration, specify software boot
parameters, ensure the appropriate software files are available,
or perform additional operating system tasks.
Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, trigger an operating system re-initialization in the DUT by
operational means such as use of the DUT's CLI or other management
interface.
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
Reporting Format
The reporting format is defined in Section 1.4.
4.2.2. Process Reset (OPTIONAL)
Objective
To characterize the time needed for a DUT to recover from a
software process reset.
Such a time period may depend upon the number and types of
processes running in the DUT and which ones are tested. Different
implementations of forwarding devices include various common
processes. A process reset should be performed only in the
processes most relevant to the tester and most impactful to
forwarding.
Procedure
First, complete some or all of the following operational tasks:
save the current DUT configuration, specify software parameters or
environmental variables, or perform additional operating system
tasks.
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Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, trigger a process reset for each process running in the DUT
and considered for testing from a management interface (e.g., by
means of the CLI, etc.).
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
Reporting Format
The reporting format is defined in Section 1.4 and is used for
each process running in the DUT and tested. Given the
implementation nature of this test, details of the actual process
tested should be included along with the statement.
4.3. Power Interruption Test
"Power interruption" refers to the complete loss of power on the DUT.
It can be viewed as a special case of a hardware reset, triggered by
the loss of the power supply to the DUT or its components, and is
characterized by the re-initialization of all hardware and software
in the DUT.
4.3.1. Power Interruption (REQUIRED)
Objective
To characterize the time needed for a DUT to recover from a
complete loss of electric power or complete power interruption.
This test simulates a complete power failure or outage and should
be indicative of the DUT/SUT's behavior during such event.
Procedure
First, ensure that the entire DUT is at a permanent state to which
it will return after the power interruption by performing some or
all of the following operational tasks: save the current DUT
configuration, specify boot parameters, ensure the appropriate
software files are available, or perform additional operating
system or hardware-related tasks.
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Second, ensure that the DUT is able to forward the traffic for at
least 15 seconds before any test activities are performed. The
traffic should use the minimum frame size possible on the media
used in the testing, and the rate should be sufficient for the DUT
to attain the maximum forwarding throughput. This enables a finer
granularity in the reset time measurement.
Third, interrupt the power (AC or DC) that feeds the corresponding
DUT's power supplies at this point. This entails, for example,
physically removing the power supplies in the DUT to later re-
insert them or simply disconnecting or switching off their power
feeds (AC or DC, as applicable). The actual power interruption
should last at least 15 seconds.
Finally, complete the characterization by recording the frame loss
or timestamps (as reported by the test tool) and calculating the
reset time (as defined in Section 1.3).
For easier comparison with other testing, 15 seconds are removed
from the reported reset time.
Reporting Format
The reporting format is defined in Section 1.4.
5. Security Considerations
Benchmarking activities, as described in this document, are limited
to technology characterization using controlled stimuli in a
laboratory environment, with dedicated address space and the
constraints specified in the sections above.
The benchmarking network topology will be an independent test setup
and MUST NOT be connected to devices that may forward the test
traffic into a production network or misroute traffic to the test
management network.
Furthermore, benchmarking is performed on a "black-box" basis,
relying solely on measurements observable externally to the DUT/SUT.
Special capabilities SHOULD NOT exist in the DUT/SUT specifically for
benchmarking purposes. Any implications for network security arising
from the DUT/SUT SHOULD be identical in the lab and in production
networks.
There are no specific security considerations within the scope of
this document.
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6. Acknowledgments
The authors would like to thank Ron Bonica, who motivated us to write
this document. The authors would also like to thank Al Morton,
Andrew Yourtchenko, David Newman, John E. Dawson, Timmons C. Player,
Jan Novak, Steve Maxwell, Ilya Varlashkin, and Sarah Banks for
providing thorough review, useful suggestions, and valuable input.
7. References
7.1. Normative References
[RFC1242] Bradner, S., "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, July 1991.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
7.2. Informative References
[IGPConv] Poretsky, S., Imhoff, B., and K. Michielsen, "Benchmarking
Methodology for Link-State IGP Data Plane Route
Convergence", Work in Progress, February 2011.
[RFC5180] Popoviciu, C., Hamza, A., Van de Velde, G., and D.
Dugatkin, "IPv6 Benchmarking Methodology for Network
Interconnect Devices", RFC 5180, May 2008.
[RFC5695] Akhter, A., Asati, R., and C. Pignataro, "MPLS Forwarding
Benchmarking Methodology for IP Flows", RFC 5695, November
2009.
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Authors' Addresses
Rajiv Asati
Cisco Systems
7025-6 Kit Creek Road
Research Triangle Park, NC 27709
USA
EMail: rajiva@cisco.com
Carlos Pignataro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
USA
EMail: cpignata@cisco.com
Fernando Calabria
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
USA
EMail: fcalabri@cisco.com
Cesar Olvera Morales
Consulintel
Joaquin Turina, 2
Pozuelo de Alarcon, Madrid, E-28224
Spain
EMail: cesar.olvera@consulintel.es
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